The utilization of phosphate ions from hydroxyapatite by oral bacteria may be significant in the carious process. Dual labeling of extracted teeth by means of neutron-irradiation (45Ca and 32P) provides a method for studying the fate of these ions in an in vitro system. To date, an isolate from deep dentinal caries (L. casei) that stores intracellular polyphosphate (polyP) granules has been used as a prototype for these studies. It has been determined that the organism utilized significant amounts of hydroxyapatite which is incorporated predominantly into the nucleic acid and polyP fractions. The calcium ions are also utilized by the bacteria and may appear in the polyP fraction. Calcium ion concentration is also high in the supernatant fluid when compared with phosphate in the same fraction. In proposed studies, the disposition of the calcium ions will be better defined by isolation of bacterial cell fractions using milder procedures. In addition, the effects of inhibition of polyP formation on the uptake of hydroxyapatite phosphate will be determined. Inhibition of this fraction may play a significant role in decreasing hydroxyapatite dissolution since approximately 50% of the cell phosphate is found in the polyP fraction and furthermore this fraction can be synthesized in the absence of cell growth. The methods of procedure developed with the prototype organism will be used to study the disposition of calcium and phosphate ions in cultures of Strep. mutans and actinomyces species described as cariogenic by other laboratories.